Magnetic visual indicating device



l 7, 1964 J. SCHALKWIJK MAGNETIC VISUAL INDICATING DEVICE- Filed May 16, 1960 FIG.3

FIG.4

FIG. 5

INVENTOR JAN SCHALKWIJK AGENT United States Patent 3,140,431 MAGNETIC VISUAL INDICATING DEVICE Jan Schalkwijk, Hilversum, Netherlands, assignor to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed May 16, 1960, Ser. No. 29,299 Claims priority, application Netherlands May 23, 1959 11 Claims. (Cl. 317171) The invention relates to an electromagnetically operating visual indicating device comprising an armature rotatable between the poles of a substantially U-shaped magnetizable yoke provided with an energizing coil, which armature contains a permanent magnetic material and the indicating member. Such a device may be used for indicating the condition of a certain electric circuit, for example, in the case of remote control and telephony.

The object of the invention is to provide an indicating device of the above type which quickly reacts to energization, automatically remains in the last operated condition, can be manufactured in a simple and cheap manner, and is of small dimensions.

According to the invention, the armature comprises a substantially non-demagnetizable permanent magnetic material having a high coercive force, preferably composed of non-cubic crystals of polyoxides of iron and at least one of the metals barium, strontium, lead and possibly calcium (Ferroxdure). The armature has two final positions which are approximately a quarter turn or more remote from one another. In each of these final positions the general direction of the magnetic flux passing from the armature of permanent magnetic material to the poles or vice versa forms an angle with the direction of magnetization of the permanent magnetic material such that the armature is held magnetically in each of these two final positions. The magnetic fluxes produced in the yoke by the magnetization of the armature in these two final positions are in opposite directions. By using a substantially non-demagnetizable permanent magnetic material for the armature, it is achieved that the polarization of this material is not altered by the magnetic field passing to and from the yoke and making an angle with it, whereby reliable operation of the device is achieved over long periods of time. Such magnetic material and their preparation are described in US. Patents Nos. 2,762,777, and 2,762,778. The magnetic material employed preferably has a composition of BaFe O and a particle size of 3-8 microns.

The armature may simply consist of a single plate of permanent magnetic material, such as Ferroxdure, painted different colors on each face. However, in a preferred embodiment of the device according to the invention, the armature is mounted between the parallel extending ends of the yoke and comprises two non-magnetic plates of different colors, between which a layer of powdered permanent magnetic material is provided. The layer of permanent magnetic material is polarized magnetically in the direction of the layer and at right angles to the rotary shaft of the armature, which in turn extends parallel to the plane of the opposing pole faces of the yoke. The non-magnetic plates are preferably of electrically insulating material in order to keep the mass of the armature as low as possible.

In another embodiment of the device according to the 3,140,431 Patented July 7, 1964 invention, the rotary axis of the armature is preferably located approximately midway between the two end faces of the yoke which are arranged substantially at right angles to one another. The armature axis extends in a direction parallel to these end faces. The permanent magnetic part of the armature comprises a member which is oblong in the direction of the rotary axis and contains said rotary shaft, said member being polarized at right angles to this axis, the armature furthermore being provided with a non-magnetic part engaging one or the other yoke end face in the final positions of the armature.

In order that the invention may be readily carried into effect, it will now be described in greater detail, by way of example, with reference to the accompanying drawing, which shows three embodiments.

FIG. 1 diagrammatically shows a side view of one embodiment,

FIG. 2 shows on an enlarged scale the armature indicating member of this device.

FIG. 3 is a side view of a second embodiment, in

I which the armature in a final position at the same time along the line VII-VII in FIG. 6.

The indicating device shown in FIG. 1 comprises a substantially U-shaped magnetizable yoke consisting of two soft-iron strips 1 and 2, the lefthand ends of which are connected together and the righthand ends of which are bent at right angles and form poles 3 and 4, between which the armature 6, rotatable around a shaft 5, is mounted. Around the strip 1 an energizing coil 7 is provided. As shown in FIG. 2, the armature comprises a magnetic layer 8 provided between and connected to two insulating plates 9 and 10, the former of which consists of White and the other of uncolored, that is to say, transparent celluloid- The layer 8 consists of a powdered permanent magnetic material composed of substantially non-cubic crystals of polyoxides of iron and at least one of the metals barium, strontium, lead and possibly calcium (Ferroxdure), and a binder. The layer 8 is polarized magnetically in a direction at right angles to the shaft 5 and in the plane of the layer, thus in the direction of the arrow P (FIG. 2) or opposite to this direction.

Between the ends 3 and 4 of the yoke, the armature 6 may assume either of two final positions, in each of which it engages these ends and is held magnetically by the magnetic flux which passes through the yoke owing to the magnetization of the layer 8. In the yoke, this flux is in opposite directions for the two final positions of the armature. These two final positions lie approximately a quarter turn from each other. The device is provided with a wall 12 having an opening 11 through which the armature 6 is visible. In the one final position, shown by the drawn outline of the armature, the uncolored plate is visible and since the layer 8 itself is dark, the opening 11 consequently is also dark. In the other final position of the armature, shown in dotted lines in FIG. 1, the white plate 9 is visible through the opening 11.

The magnetic part of the armature, in this case the layer 8, is magnetized at right angles to the shaft 5. The position which the armature will assume when energized by the coil 7 then depends upon the direction of the current in this coil. As already stated above, the armature remains in the occupied final position when the energization is removed from coil 7. The armature being comparatively small andhaving a small mass, a

short energization is sufficient to bring the armature from one final position to the other. Thus, a short positive pulse to the coil 7 will flip the armature from the white to the black position, and a short negative pulse will flip it back to the white position. In the embodiment shown in FIG. 3, corresponding largely to that of FIG. 1, the ends of the magnetizable strips 1 and 2 are not bent, so that the longitudinal direction of the device is at right angles to the wall 12. A further difference with the embodiment as shown in FIG. 1 is that the armature 36 in the final position as shown forms an electric connection between two rigid electric contacts 31 and 32 provided in an insulating manner on an end portion of the strips 1 and 2, so that the device may also exert an electric switching function. In order for the armature to be able to establish the connection between the contacts 31 and 32, said armature is provided on the outside with a conductive coating of thin metal sheet. Naturally, this coating should not be magnetic and should be of significantly different color on both sides of the armature so as to render the visual indication through the opening 11 in the wall 12 possible. The armature 36 of the device shown in FIG. 3 encloses the shaft 5 with sufficient play to enable it to co-operate simultaneously with the two contacts 31 and 32. To render this searching possible, the shaft 5 may also bear in relatively roomy cu s.

Ihe yoke may also comprise on the end portions two further rigid electric contacts provided in an insulating manner, which are adapted to be connected electrically by the armature in the other final position of this armature 36, which is not shown.

The devices shown in FIGS. 1 and 3 are preferably protected against dust by a hood, for example, of syn-, thetic material, which is not shown.

The armature 6 (FIG. 1) and also the armature 36 (FIG. 3) may be manufactured in the following manner. A U-shaped permanent magnet 40 (FIG. 4) comprises, between the limbs and at a small distance from the ends thereof, a non-magnetic, for example insulating, supporting layer 41 which may fillzthe whole interior of the magnet 40 and which is provided, at the level of the end of the magnet 40, with a cavity 42, the dimensions of which correspond to those of the armature to be manufactured. In this cavity 42 first one of the celluloid plates 9 and 10 is laid, then a wire 5 is laid at right angles across this plate and then magnetized Ferroxdure powder is sprinkled on it. The particles of the layer formed by the Ferroxdure powder, which layer may be about 1 mm. thick, orientate themselves upon tapping against the magnet. hardenable adhesive is applied on the layer 8. This adhesive may consist, for example, of an ethoxylene resin with a hardening agent or a cellulose lacquer. The wire 5' is pretreated, for example greased, in a manner such that the adhesive does not adhere to it. After the adhesive has penetrated into the layer 8, the other of the celluloid plates 9 and 10 is laid on top of it and kept under pressure until the adhesive has hardened. After removing the thus formed armature from the cavity, the wire 5 is replaced by the shaft 5, so that the now finished armature 6 may be used between the poles 3 and 4 of the device shown in FIG. 1. In order to use the armature manufactured in the above manner in a device as Then a small quantity of fluid,

shown in FIG. 3, it is additionally required to provide said armature with a conductive coating of different color on both sides.

The embodiment shown in FIGS. 5 to 7 comprises a magnetic yoke 50 having limbs 51 and 52. The limb 51 is provided with an energizing coil 57. The other limb 52 has a first portion which extends parallel to the limb 51 and beyond the end of limb 51 there is a member 54 bent at right angles to form a pole, the direction of which is at right angles to the longitudinal direction of the limb 51. On the line connecting the end faces of the limb 51 and the pole 54, there is located approximately midway the rotary shaft 55 of a rotatable armature 56. The armature comprises a cylindrical piece 58 of Ferroxdure containing said rotary shaft, which piece is mounted in an insulating moulding 60, for example, of polyamide. This moulding comprises, at some distance from the shaft 55, a plate-shaped member 61 extending parallel to said shaft. In the end position of the armature 56 shown in FIG. 5, wherein one side of the moulding engages the end face of the pole 54, member 61 extends parallel to this pole. In the other end position of the armature 56, shown in FIG. 6, in which end position an opposite surface of the molding 60 engages the end of the limb 51, the member 61 extends parallel to the longitudinal direction of the limb 51. The outer surface of the plate-shaped member 61 is provided with a lightcolored layer 62, for example, of white lacquer. Viewed from the right, the device shows a white surface in the end position of the armature shown in FIG. 5, whereas in the end position shown in FIG. 6, this white surface is no longer visible.

The cylindrical member 58 of the armature exhibits end planes which are oblique to the shaft 55 thereby anchoring the member 58 in the molding 60. The member 58 is polarized magnetically at right angles to the direction of the shaft 55 in a manner such that the direction of magnetization is at right angles to the lightcolored front face of the member 61, for example, corresponding to the direction of the arrow Q in FIGS. 5 and 6. As a result of this construction, the armature is held magnetically in either of the two end positions because the general direction of the magnetic flux travelling from the permanent magnetic part 58 to an end of the yoke, or vice versa, forms an angle with the direction of polarization Q. In these end positions, a magnetic moment is exerted on the armature which maintains the armature in the last occupied end position.

The armature 56 is supported in a rotatable manner by two taps 63 shown in FIG. 7 only. In this case also, the occupied end position of the armature is determined by the direction of a preceding energizing current in the coil 57.

What is claimed is:

1. An electromagnetic indicating device comprising an electromagnetic system having yoke and conductor means associated therewith, said yoke means having first and second pole members disposed substantially at right angles to each other and said conductor means providing at said first and second pole members first and second magnetic poles of opposite polarity, respectively, for the establishment therebetween of a magnetic field having a direction responsive to the relative electric polarity of a predetermined electric signal applied to said conductor means, a substantially cylindrical shaped rotatable member of permanent magnetic material having a predetermmed permanent north and south pole characteristic substantially transverse to the longitudinal axis thereof, said rotatable member'being rotatable about said longitudinal axis in response to the relative direction of said magnetic field, said longitudinal axis having its center located between said pole members, and means to arrest the rotation of said rotatable member at first and second indicating positions for predetermined and opposite types, re-

spectively, of said signal polarity, said means to arrest comprising a nonmagnetic member connectively disposed about said rotatable member, said non-magnetic member engaging said yoke means at said first and second pole members thereof in said first and second positions, respectively.

2. An electromagnetic indicating device according to claim 1 wherein said non-magnetic member further comprises a visual indicator member having first and second indicating characteristics at said first and second positions, respectively.

, 3. An electromagnetic indicating device comprising an electromagnetic system having yokeand conductor means associated therewith, said yoke means having first and second pole members disposed at substantially right angles to each other, said conductor means providing at said first and second pole members first and second magnetic poles of opposite polarity, respectively, for the establishment therebetween of a magnetic field having a direction responsive to the relative electric polarity of a predetermined electric signal applied to said conductor means, a substantially cylindrical shaped rotatable member of permanent magnetic material of high coercive force having a predetermined permanent north and south pole characteristic substantially transverse to the longitudinal axis thereof, said rotatable member being rotatable about said longitudinal axis in response to the relative direction of said magnetic field, said longitudinal axis having its center located substantially midway between said pole members, and means to arrest the rotation of said rotatable member at first and second positions for predetermined and opposite types, respectively, of said signal polarity, said means to arrest comprising a non-magnetic member of a plastic-like material connectively disposed about said rotatable member, said non-magnetic member engaging said yoke means at said first and second pole members thereof in said first and second positions, respectively.

4. An electromagnetic indicating device according to claim 3 wherein said non-magnetic member further comprises a visual indicator member having first and second indicating characteristics at said first and second positions, respectively.

5. An electromagnetic indicating device comprising an electromagnet having yoke means and an energizing winding disposed thereon, said yoke means having first and second opposed pole pieces disposed substantially at right angles to each other, said electromagnet providing at said first and second pole pieces magnetic poles of opposite polarity thereby establishing between said poles a magnetic field having a direction responsive to the relative electric polarity of a predetermined electric signal applied to said energizing winding, a rotatable permanently magnetized member symmetrically shaped about its longitudinal axis and having a predetermined permanent north and south pole characteristic substantially transverse to said longitudinal axis, means for rotatably supporting said rotatable member for rotation about its longitudinal axis in response to the relative direction of said magnetic field, said rotatable member being symmetrically located between said pole pieces to provide a substantially uniform reluctance path between said pole pieces for all positions of said rotatable member, and a non-magnetic indicating member connectively disposed about said rotatable member and extending therefrom to arrest the rotation of said rotatable member at first and second indicating positions for predetermined and opposite polarities of said electric signal, said first and second indicating positions corresponding to engagement of said non-magnetic member with said yoke means at said first and second pole pieces, respectively.

6. An electromagnetic indicating device comprising an electromagnet having yoke means and an energizing winding disposed thereon, said yoke means having first and second opposed pole pieces disposed substantially at right angles to each other, said electromagnet providing at said first and second pole pieces magnetic poles of opposite polarity thereby establishing between said poles a magnetic field having a direction responsive to the relative electric polarity of a predetermined electric signal applied to said energizing winding, a cylindrical permanently magnetized rotatable member rotatably supported about its longitudinal axis for rotation upon energization of said electromagnet, said rotatable member having a predetermined permanent magnetic axis substantially transverse to the longitudinal axis thereof so that said rotatable member will rotate about said longitudinal axis in response to the relative direction of said magnetic field, said rotatable member being symmetrically located midway between said pole pieces to provide a substantially uniform reluctance path between said pole pieces for all positions of said rotatable member, and a non-magnetic indicating member connectively disposed about said rotatable member and extending therefrom to arrest the rotation of said rotatable member at first and second end positions for predetermined and opposite polarities of said electric signal, said first and second end positions corresponding to engagement of said non-magnetic member with said yoke means at said first and second pole pieces, respectively.

7. Apparatus according to claim 6 wherein the longitudinal axis of rotation of said rotatable member is located at the mid-point of a line connecting the end surfaces of said pole pieces.

8. Apparatus as described in claim 6 wherein the longitudinal axis of said rotatable member extends substantially parallel to the end faces of said pole pieces.

9. Apparatus as described in claim 6 wherein the magnetic axis of said rotatable member forms an acute angle with the direction of said magnetic field at each of said first and second end positions whereby said rotatable member is subjected to a magnetic torque which holds said member in said end position.

10. An electromagnetic indicating device comprising an electromagnet having yoke means and an energizing winding disposed thereon, said yoke means having first and second opposed pole pieces disposed substantially at right angles to each other, said electromagnet providing at said first and second pole pieces magnetic poles of opposite polarity thereby establishing between said poles a magnetic field having first and second diametrically opposite directions responsive to the relative electric polarity of a predetermined electric signal applied to said energizing winding, a cylindrical permanently magnetized rotatable member having a predetermined permanent northsouth magnetic axis substantially transverse to the longitudinal axis thereof, means for rotatably supporting said rotatable member for rotation about its longitudinal axis to first and second end positions in response to the relative direction of said magnetic field, said rotatable mem ber being symmetrically located between said pole pieces and having a non-magnetic indicating member disposed thereon, said non-magnetic member engaging said yoke means at said first pole piece in said first end position and engaging said second pole piece in said second end position, the magnetic axis of said rotatable member in each of said first and second end positions being substantially parallel to the longitudinal axis of the non-engaged pole pieces at said end position.

11. An electromagnetic indicating device comprising an electromagnet having yoke means and an energizing winding disposed thereon, said yoke means having first and second opposed pole pieces disposed substantially at right angles to each other, said electromagnet providing at said first and second pole pieces magnetic poles of opposite polarity thereby establishing between said poles a magnetic field having a direction responsive to the relative electric polarity of a predetermined electric signal applied to said energizing winding, a cylindrical permanently magnetized rotatable member rotatably supported about its longitudinal axis for rotation upon energization of said electromagnet, said rotatable member having a predetermined permanent magnetic axis substantially transverse to the longitudinal axis thereof so that said rotatable member will rotate about said longitudinal axis in response to the relative direction of said magnetic field, said rotatable member being symmetrically located midway between said pole pieces to provide a substantially uniform reluctance path between said pole pieces for all positions of said rotatable member, and a non-magnetic indicating member connectively disposed about said rotatable member and extending therefrom to limit the rotation of said rotatable member to a 90 degree are between first and second end positions, said first and second end positions corresponding to engagement of said non-magnetic member with said yoke means at said first and second pole pieces, respectively.

References Cited in the file of this patent UNITED STATES PATENTS Wallace Ian. 23, 1951 Brookes et al Mar. 24, 1953 Hatton Apr. 3, 1956 Babcock Feb. 3, 1959 Ugon Oct. 13, 1959 Stein Jan. 12, 1960 Fry Feb. 2, 1960 Williams Nov. 8, 1960 Bloechi Mar. 13, 1962 FOREIGN PATENTS Switzerland Dec. 16, 1953 

1. AN ELECTROMAGNETIC INDICATING DEVICE COMPRISING AN ELECTROMAGNETIC SYSTEM HAVING YOKE AND CONDUCTOR MEANS ASSOCIATED THEREWITH, SAID YOKE MEANS HAVING FIRST AND SECOND POLE MEMBERS DISPOSED SUBSTANTIALLY AT RIGHT ANGLES TO EACH OTHER AND SAID CONDUCTOR MEANS PROVIDING AT SAID FIRST AND SECOND POLE MEMBERS FIRST AND SECOND MAGNETIC POLES OF OPPOSITE POLARITY, RESPECTIVELY, FOR THE ESTABLISHMENT THEREBETWEEN OF A MAGNETIC FIELD HAVING A DIRECTION RESPONSIVE TO THE RELATIVE ELECTRIC POLARITY OF A PREDETERMINED ELECTRIC SIGNAL APPLIED TO SAID CONDUCTOR MEANS, A SUBSTANTIALLY CYLINDRICAL SHAPED ROTATABLE MEMBER OF PERMANENT MAGNETIC MATERIAL HAVING A PREDETERMINED PERMANENT NORTH AND SOUTH POLE CHARACTERISTIC SUBSTANTIALLY TRANSVERSE TO THE LONGITUDINAL AXIS THEREOF, SAID ROTATABLE MEMBER BEING ROTATABLE ABOUT SAID LONGITUDINAL AXIS IN RESPONSE TO THE RELATIVE DIRECTION OF SAID MAGNETIC FIELD, SAID LONGITUDINAL AXIS HAVING ITS CENTER LOCATED BETWEEN SAID POLE MEMBERS, AND MEANS TO ARREST THE ROTATION OF SAID ROTATABLE MEMBER AT FIRST AND SECOND INDICATING POSITIONS FOR PREDETERMINED AND OPPOSITE TYPES, RESPECTIVELY, OF SAID SIGNAL POLARITY, SAID MEANS TO ARREST COMPRISING A NONMAGNETIC MEMBER CONNECTIVELY DISPOSED ABOUT SAID ROTATABLE MEMBER, SAID NON-MAGNETIC MEMBER ENGAGING SAID YOKE MEANS AT SAID FIRST AND SECOND POLE MEMBERS THEREOF IN SAID FIRST AND SECOND POSITIONS, RESPECTIVELY. 